The number of different radios in mobile communication devices is steadily increasing to facilitate more flexible connectivity and a broader range of services. Cellular access alone is no longer sufficient, but new wireless technologies are integrated to communication devices now and especially in the future to enable novel connectivity solutions. Integration of multiple radios into a single terminal, however, introduces a serious integration challenge that is becoming more pronounced as the number of radios increases. One element of the integration challenge is the appropriate handling of simultaneous operation of radios. It is quite evident that users are willing to use different radios at the same time, like using a headset employing wireless Bluetooth® technology during a GSM phone call, and using a wireless local area network (WLAN) connection for Internet surfing, for example.
If there are two or more operational radio connections from one communication device, the connections may very well interfere with one another. Even if the connections are not operating on the same frequency band, they may still interfere with each other due to the non-idealities in the components of the communication device. The components may introduce spectral leakage, and the selectivity of receivers may not be ideal, meaning that they may also receive signal components belonging to a signal other than the desired one.
If there is a number of connections simultaneously operating on the same band, interference they cause to one another is much more severe than if they were operating on separate bands. Especially on the 2.4 GHz unlicensed Industrial, Scientific and Medical (ISM) band there may be several connections, for example Bluetooth® and wireless local area network (WLAN) connections, operating on the same band simultaneously. These connections cause inter-system interference to one another, which may result in a degraded quality of service. If there are two active connections on the same band operating from the same communication device, these two connections may very well interfere with each other severely, or the connections may even block each other's usage totally. This may happen because both of the connections operate from the same communication device, and thus the radio transceivers may be located within a few centimeters from each other. They may also be using the same radio components, like an antenna, for instance.